Users are increasingly demanding functionalities beyond merely recognizing a touch to the surface of the touch-sensitive device. Such other functionalities include handwriting recognition and direct note taking (using, for example, a stylus). Such functionalities are generally provided in so-called digitizing systems.
Digitizing systems having position-dependent indicia detected by an image sensor in a stylus are commercially available. Anoto Group AB sells a stylus that detects indicia printed on an opaque paper or cardboard substrate. Reference is made to US Patent Publication No. 2010/0001962 (Doray), which describes a multi-touch display system that includes a touch panel having a location pattern included thereon.